The effect of endogenous antibody on insulin-assay in the newborn infants of diabetic mothers.

Abstract

Extract: The immunoassay of insulin in blood of infants born to diabetic mothers is complicated by the presence of anti-insulin antibodies. Twelve infants born to diabetic mothers receiving insulin up to the time of delivery (Group 1) and two born to diabetic mothers maintained by dietary restrictions without insulin (Group 2) were studied. Four infants born to normal mothers served as controls (Group 3). The range of values in cord blood of infants of Group 1 was 80-1000 (median 550) (method of HALES and RANDLE) and 33 to 72.5 % (median 53.8) ofthe radioactivity was bound to plasma proteins. In one infant in Group 1, maximum amount of the radioactivity (42.3 %) from labeled insulin (43 %) was bound to a γ-globulin (0% in Groups 2 and 3). In one infant in Groups 2 and 3 maximum amount of radioactivity was in the α-globulin fraction (44.1 and 35.3 % respectively). At 120 minutes after birth, glucose, 0.5 gm/kg body weight, was infused quickly into the umbilical vein of 6 patients in Group 1 and the two in Group 2. In the former, insulin levels rose significantly, 1- to 4-fold, despite the elevated level at commencement of infusion; in the latter, the insulin levels rose 4-fold in one case and 18-fold in the second. The amount of anti-insulin antibody present in serum of infants in Group 1 did not change significantly during the first 240 minutes after birth; neither was it affected by the administration of glucose and the subsequent appearance of endogenous insulin. Speculation: Although the infant born to a diabetic mother has elevated levels of insulin and circulating anti-insulin antibodies, his ability to release insulin following a glucose challenge appears unimpaired. This combination of abnormalities suggests an alteration in glucose homeostasis, but fails to explain the hypoglycemia commonly seen in such infants, unless the anti-insulin antibodies do not interfere with the hypoglycemic effects of insulin.